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Enantioselective homocrotylboration of aliphatic aldehydes
Hongkun Lin1, Wenbo Pei, Hao Wang
1Department of Chemistry, Brandeis University, Waltham, Massachusetts 02454-9110, United States.
Abstract:
A practical route to optically pure syn-homocrotylation reagents is described, including highly diastereo- and enantioselective preparation of numerous syn-homocrotyl products, as well as several matched mismatched pairs. NMR experiments suggest that the active homocrotylating species is a cyclopropylcarbinyldichloroborane generated by chloride exchange from the PhBCl(2) activator. Computational studies support the intermediacy of chloroboranes and suggest that homoallyl/homocrotyl transfers occur through Zimmerman-Traxler transition states.
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